Automatic telephone system



T. G. MARTIN AND E. JACOBSEN.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED FEB. 14, I917.

1 347, 584:; Patented July 27, 1920.

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UNITED STATES PATENT OFFICE.

TALBOT G. MARTIN, OF CHICAGO, AND EMIL JACOBSEN, F EVANSTON, ILLINOIS,

ASSIGNORS TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPO- RATION OE ILLINOIS.

Specification of Letters Patent.

Patented July 27, 1920.

Application filed February 14, 1917. Serial No. 148,478.

To all whom it may concern:

Be it known that we, TALBOT G. MARTIN .and Earn. JAcousEN, both citizens of the United States of America, and residents, respectively, of Chicago, Cook county, lllinois, and Evanston, Cook county, Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

Our invention relates in general to automatic telephone systems, but is particularly well adapted for use in small exchanges of this character which are commonly known as private branch exchanges. WVhere the number of subscribers is small, the expense of providing the usual alternating current ringing apparatus is out of proportion to the cost of the remainder of the exchange equipment, and we have designed, therefore, a direct current ringing system, which constitutes the principal feature of the invention. Additional novelty is believed to exist in the new connector circuit designed to provide for certain desirable operating features besides the one mentioned, all of which will be described and explained fully hereinafter, reference being had to the accompanying drawing.

In the drawing we have shown diagrammatically private branch exchange equipment embodying our invention, through the medium of which a complete connection has been established between a calling substation A and a called substation A. The apparatus included in the connection comprises the individual line switch C and the connector switch E. The line switch C is associated with the line of the called substation A, while the master switch D is provided for the purpose of controlling the trunk selecting operations of the line switches G and C and other similar line switches.

The substation A may be of any approved automatic type such, for example, as the substation shown in British patent to Martin, #1419 of 1910. As represented herein it comprises essentially the receiver 2, transmitter 3, switch-hook 4, and ringer 5, together with a pair of impulse springs 7 and 8 controlled by an impulse wheel 9 through the medium of a finger hole dial (not shown). The ringer 5 may be an ordinary direct current vibratory bell, either of the type in which the operating magnet short circuits its winding, or of the tvpe in which the operating magnet controls a circuit interrupter, the latter type being preferable, however; and is connected from the lower hook switch contact spring to ground. It should be mentioned that the r nger magnet is desirably of somewhat higher resistance than is usually the case with direct current bells in order to enable it to operate on the comparatively small amount of current supplied over the line from a connector switch at the exchange in a manner to be explained hereinafter.

The line conductors 12 and 13 of the substation A are connected at the exchange to the individual line switch C which is of the general type of line switch disclosed in the British patent to James, #26301 of 1906; being, however, of the particular type shown in U. S. Letters Patent #1078690, granted Jan. 17 1912, to Frank Newforth. Through the medium of line switch C the line of connector switches.

The line switches shown and a plurality of similar switches are controlled in their trunk selecting operations by means of the master switch D. This latter is of the general type of master switch disclosed in the above mentioned British patent to James, #26301 of 1906; being, however, more nearly of the particular type disclosed in the British patent to Martin, #1419 of 1910, also previously referred to. As is well known, the function of the master switch is to maintain the plungers of all idle line switches which it controls in position before the terminals of an idle trunk line.

One of the trunk lines to which the line switch C has access is shown in the drawing as extending to the connector switch E. The connector E is in general similar in construction to the switch shown in U. S. Letters Patent N0. 815176, granted March 13, 1906, to Keith, Erickson, and Erickson, except that the side switch and private magnet are omitted, and the circuits are revised in accordance with the two-wire system of control. Further modifications in the circuits, provided in accordance with our invention, will be described in detail hereinafter.

The substation A and the line switch C may be in all respects similar to the substation A and the line switch C.

There has been shown throughout the drawing a plurality of batteries, B, B etc., but it is to be understood that thereis preferably but one battery having its positive pole grounded. The reference character S indicates a busy signaling machine, which may be of the usual type common in other automatic systems.

The operation of the system is as follows: When the subscriber at substation A removes his receiver to initiate the call an energizing circuit is completed over the line conductors 12 and 13 for the line relay 14 of the line switch C. Upon attracting its armature, the line relay 14 closes a circuit for the pull-in winding 18. Upon energizing, the pull-in winding energizes its core sufficiently to operate both the plunger arm 15 and the cut-off armature 16; the former through the medium of its plunger (not shown) forcing the bank springs 22-25, inclusive, into engagement, respectively, with contacts 26-29, inclusive; and the latter disconnecting the line conductors 12 and 13 from ground and battery, respectively. By the engagement of bank springs 22 and 25 with their associated bank contacts 26 and 29, the line conductors l2 and 18 are extended to the double wound line relay 40 of the connector E.

The line relay 40 is accordingly energized over the calling line circuit and upon attracting its armature 51 closes a circuit for the slow acting release relay 41. Upon energizing in turn, the relay 41 completes a holding circuit for the line switch C which may be traced as follows: ground at G working contact of armature 57 and the said armature, conductor 58, contact 27, bank spring 23, and the holding winding 17 to battery B. Since the line relay 14 is slow acting it retains its armature to maintain the pull-in winding energized until after the above holding circuit has been established. A branch of the holding circuit extends by way of conductor 19 to multiple test contacts in the banks of connector switches having access to the line of substationA, whereby a ground potential on these test contacts the said line is made busy. By the engagement of bank spring 24 with contact 28 the master switch D is operated in well known manner to advance the plungers of all the remaining idle line switches into position before the terminal of the next idle trunk line.

The foregoing operations have occurred in response to the removal of the receiver at substation A. The calling subscriber may now proceed to manipulate, his calling device in accordance with the first digit of the desired number, thereby producing in the usual and well known manner a series of interruptions in the line circuit. At each interruption the line relay 4O deenergizes momentarily and sends an impulse of current to the vertical magnet 49 over the following path: ground at G armature 51 and its resting contact, armature 52 and its working contact, ofi' normal springs 54 and 56, winding of low resistance slow acting relay 42, and winding of vertical magnet 49 to battery B In response to these impulses the vertical magnet operates to raise the switch shaft step by step until the wipers 90, 91, and 92 arrive at the horizontal level of bank contacts in which are located the terminals of the line of substation A. Relay 42-is energized in series with the vertical magnet and retains its armature during the series of impulses, thereby preventing the opening of the vertical magnet circuit by the shifting of the off normal springs, which operation occurs as soon as the shaft leaves normal position.

The calling subscriber may now call the units or final digit in the desired number,

thereby producing as before a series of interruptions in the line circuit.. Now, however, the oif normal springs being in the position shown in the drawing, and the relay 42 having deenergized, the line relay transmits a series of impulses to the rotary magnet 50 over the following path: ground at G armature 51 and its resting contact, armature 52 and its working contact, ofi' normal springs 54 and 55, armature 53 and its resting contact, armature 60 and its resting contact, the resting contact of armature 67 and the said armature, and the winding of rotary magnet 50 to battery B The rotary magnet responds to the impulses of current in its circuit to rotate the wipers 90, 91, and 92 until they arrive at bank contacts 93, 94, and 95, which form the terminal of the line of substation A in the bank of the connector E. It will be noted that a branch of the rotary magnet circuit extends from the resting contact of armature 60 through.

the winding of the slow acting relay 44 to battery 13. It follows that relay 44 will be energized in parallel with the rotary magnet during the rotation of the switch, and since it is slow acting, it retains its armatures attracted continuously. Bythe attraction of the upper armature 64 the test wiper 91.is connected to the upper winding of relay 48 as follows: test wiper 91, arma-- ture 4 and its working contact, resting contact of armature 68 and the said armature, a section of the upper heavy talking conductor, and the upper winding of relay 43 to contact.

The switch wipers having been rotated into connection with the desired line, the line of substation A, the operations now depend on whether or not that line is busy. Assuming the line to be idle, the test contact 94 will be clear of ground, the relay 43 will remain inoperative, and upon the decliergization of relay 44 the following circuit will be closed: grounded conductor 58, armature 59 of relay 43 'and its resting con tact, winding 46 of relay 45, resting contact of armature 64 and the said armature, test wiper 91, test contact 94, and the holding winding 17' of line switch C to battery B Relay 45 and the holding winding 17 are energized in series, the latter operating the cut-off armature 16' to clear the line of substation A from battery and ground connections in the line switch. Relay 45, upon energizing, closes a locking circuit for itself by way of its armature 66, inner working contact, and winding 47 to battery B At the same time at the outer working contact of armature (36, the conductor 58 is connected direct to the test wiper 91. Further results of the energization of relay 45 are the closure of the line conductors at armatures 65 and 69, the opening of the rotary magnet circuit at armature 67 and the breaking of the previously described test circuit at armature 68.

The required connection has now been established. The signaling of the called subscriber is accomplished in the following manner: Each telephone number may have an extra final digit, preferably the digit 0, in addition to the ones necessary to control the line selection. Vhen the calling subscriber dials this last digit, the line relay 40 transmits a series of ten impulses to the slow acting relay 44 over a circuit previously described. Since the circuit of the rotary magnet 50 has been broken at armature 67 of relay 47 it does not respond to these impulses. The relay 44, however, is operated and retains its armatures attracted throughout the series of impulses, thereby closing at its armature 63 a signaling circuit which may be traced as follows: ground at G, winding of ringer 105 and the interrupter contact thereof, hook switch contacts, line conductor 112, bank contact 95,

wiper 92, working contact of armature (39 and the said armature, armature 63 and its working contact, and the upper winding of relay 43 to battery 13''. Upon the closure of the above circuit the ringer 105 at substation A is actuated to signal the called sub-,

scriber, relay 43 remaining quiescent. In case a prompt answer is not received the bell can be rung again by calling another digit, and the subscribers are desirably so in-l structed.

When the subscriber at substation A removes his receiver to answer the call, a circuit is completed over the heavy line conductors (it being assumed that relay 44 is de'e'nergized) for both windings of relay 43 in series, and the said relay is energized. At

the rear contact of armature 60 the circuit of relay 44 is broken so that it cannot be energized by another operation ofthe dial. The two subscribers are now connected for conversation. Talking battery for the transmitter at substation A is supplied from the windings of the line relay 40, while the transmitter at substation A is supplied from the windings of relay 43. The path for voice currents is indicated by the heavy conductors, and will be readily understood without further explanation.

When the conversation is finished both subscribers will replace their receivers. By the replacement of the receiver at substation A the circuit of the line relay 40 is broken. Upon deenergizing, line relay 40 breaks the circuit of release relay 41 which upon deenergizing in turn removes ground from the holding circuit extending back to line switch C, and also closes a circuit for the release magnet 48. By the former operation the line switch is allowed to restore to normal by withdrawing its plunger from the bank, while the energization of the release magnet 48 results in the restoration of the connector to normal. These operations are well understood and need no fur ther comment.

It will now be described briefly how the connector E operates when it is attempted to establish connection with a busy line. For this purpose it will be assumed that the line of substation A was busy when called, in which case the test'contact 94 would have a ground potential upon it. Under these circumstances, when the connector wipers are rotated into engagement with the contacts 93, 94, and 95, the relay 44 being energized during the rotation as previously described. as soon as the test wiper 91 arrives attest contact 94 the relay 43 will be energized which will now be pointed out. At the resting contact of armature 59 the conductor 58 is disconnected from the winding 46 of relay 45, and at the working contact of the same armature a locking circuit is prepared which, upon the deenergization of relay 44, is completed over the following path: grounded conductor 58, armature 59 and its working contact, contact 70 and the contact spring in engagement therewith, resting contact of armature 68 and the said a called line, a direct current ringer at the over a circuit already traced with results 3. In a telephone system,a calling and s5 substation on the called line, an automatic connector switch controllable over the calling line to establish a talking-circuit between] the calling and the called line, a

called line after thetalking circuit is established, and means controlled by the calling subscriber after the talking circuit is established for shifting one of the called line conductors from one terminal of said source armature, and the upper winding of relay to the other to operate said ringer.

43 to battery B. Relay 43 is thus locked in energized position until the connector is 1 released, and the relay 45 is prevented from ing contact of armature 60, and the con- 'called line. 4 .ation of relay 43 at thls time are the openenerglzing to establish connection with the Further results of the opering of the rotary magnet circuit at the restnection of a lead from the busy signaling machine S to the lower heavy line conductor. The latter connection may be traced as follows: lower heavy line conductor, resting contact of armature 63 and the said armature, armature 69 and its resting contact, 1

and the working contact of armature '61 and the said armature to the busy signaling machine S. By the transmission of a distinctive tone to the calling subscriber, he is informed that the line with which he is attempting to connect is busy, whereupon he will replace his receiver and the line switch and connector will be released as previously explained. v

Having described our invention what we consider to be new and desire to have pro-- tected by Letters Patent will be pointed out in the appended claims.

What we claim as our invention is:

1. In a telephone system, subscribers lines having direct current signaling equipment, automatic connector switches at the exchange, means whereby calling subscribers can extend a talking circuit to said connector switches and can thereafter operate said switches to extend said talking circuit to called lines, and means in each switch controllable by the calling subscriber after said talking circuit is extended to a called line to operate the signaling equipment on the connected called line.

2. In a telephone system, a calling and a called line, a direct current ringer at the substation on the called line, an automatic connector switch controllable over the calling line to establish a talking circuit between the calling and the called line, a source of direct current, and means in said connector controlled by the calling subscriber after the talking circuit is established for connecting said source with the called line to operate said ringer;-

4. In a telephone system, a calling and a called line, a direct current ringer at the substation on said'line, a connector switch, means for operating said connector to establish a talking circuit between said lines, and means inrsaid connector operable'thereafter for supplying current to said ringer.

. 5. In a telephone system, a calling and :1 called line, a direct current ringer at the substation on said called line, a connector switch, means for operating said connector to establish a talking'circuit between said lines, said operating means under the control of the subscriber on the calling line, and additional means under the control of the said subscriber after said talking circuit is established for supplying current to said ringer.

6. In a telephone system, a link circuit comprising two talking conductors, a grounded battery in bridge of said conductors, means for connecting said link at one .end wlth a calling subscribers line and at which the subscribers lines are each pro-' vided with a signal bridged from one side of the line to ground, and comprising link circuits for establishing a talking circuit be tween a pair of said llnes', together with a grounded battery and means in each link controlled by the calling subscriber after the talking circuit has been established for connecting the ungrounded pole of said battery to the signaling conductor of a connected line.

8. In a telephone system, a temporarily established talkingcircuit between a calling and a called line including an automatic connector switch, a grounded battery, a di-v rect current signaling device connected from one conductor of the called line to ground, and means in said connector after said talk- 70 source of direct current brid ed across the ing circuit is established for connecting said zrin'ger on the called line, and signaling conductorto the ungrounded pole of-said battery to operate said signaling device.

9. In a telephone system, a temporarily established talking circuit between a calling and a called line including an automatic connector switch, a grounded battery, a di-.

10. In a telephone system, a calling and a. called line, a connector switch, means for operating said switch to establish a talking circuit between said lines, a grounded battery, connections in said switch from the two conductors of said called line to the grounded and non-grounded poles of said battery, respectively, a direct current ringer at the substation on said called line connected from the grounded line conductor to ground, and means after said talking circuit is established for shifting said conductor to the non-grounded pole of said battery to operate said ringer.

11. In a telephone system, a callingand called line, a direct current ringer at the substation on said called line connected from one of the line conductors to ground, a connector switch, means controlled over the calling line for operating said connector to establish a talkingcircuit between said lines, a grounded battery in bridge of said line after said talking circuit is established, the grounded pole of the battery being connected to the grounded line conductor, and a relay in said connector for shifting said conductor after said talking circuit is established to the other pole of said battery to operate said ringer.

12. In a telephone system, a calling and a called subscribers line, an automatic connector switch, means for extending a talk ing circuit to said connector, means for producing series of current impulses in the calling line to operate said connector to extend said talking circuit to a called line, and means thereafter in the connector responsive to a subsequent series of impulses from said second means to connect a source of current with the called line to operate a direct current signal at the substation thereon.

13. In a telephone system, a calling and a called subscribers line, an automatic connector switch, means for extending a talking circuit to said connector, means for producing series of current impulses in the calling line to operate said connector to extend said talking to a called line, a direct current means in said connector after said talking circuit is established responsiveto a subsequent series of impulses to operate said rlnger.

14, In a telephone system, a calling and a called subscribers line, an automatic connector switch, means for extending a talking circuit to said connector, means for producing series of current impulses in the calling line to operate said connector to establish a talking circuit between said lines, a direct current ringer connected from one conductor of the called line to ground, a grounded battery at the exchange, and means in said connector after said talking circuit is established responsive to a subsequent series of impulses to connect said conductor to the ungrounded pole of said battery to operate said ringer.

15. In a telephone system, a calling and a called line, an automatic switch comprising talking conductors for connecting said lines, a relay bridged across said conductors in series with a battery, a direct current ringer at the substation on the called line, and means for supplying current from said battery through a winding of said relay to the connected called line both for talking and for operating said ringer.

16. In a telephone system, a calling and a called subscribers line, an automatic connector switch for connecting said lines, and a combination battery supply and test relay insaid connector, said relay supplying current to the called line for talking and ringing purposes.

17. In a telephone system, a calling and a called subscribers line, an automatic switch comprising a pair of talking conductors and instrumentalities for connecting. said lines thereover, a battery supply relay normally connected in bridge of said conductors, and a circuit for testing the called line prior to connecting therewith including a winding of said relay.

18. In a telephone system, a calling and a called subscribers line, an automatic switch comprising a pair of talking conductorsand instrumentalities for connecting said lines thereover, a battery supply relay normally connected in bridge of said conductors, a test wiper in said switch, and means for temporarily connecting said wiper to one of said conductors to permit the said relay to test the called line.

19. In a telephone system, a calling and a called line, an automatic switch comprising line wipers for connecting said lines, a test wiper in said switch, a relay, means for energizing said relay via said line wipers if the called line is idle, and means for energizing said relay via said test wiper if the called line is busy, said relay supplying current to the called line for talking and ringing purposes.

for supplying signaling and talking battery to the called line when idle, said relay sup.- plying battery to said test wiper when the called line is busy.

21. In a telephone system, a calling and a called line, an automatic switch having signaling current through its winding to said called line via one of said line Wipers,

and means for energizing said relay via said test wiper if the called line is busy.

. Signed by me at Chicago, Cook county, Illinois, this Gthday of F eb., 1917.

' TALBOT G. MARTIN. Signed by me at Chicago, Cook county, Illinois, this 6th day of Feb. 1917 EMIL jAcoBsEN. 

